Conventionally, agricultural balers comprise a wheeled frame which is towed by a tractor over a field to pick up hay, straw or silage grass and to feed such crop material to a baling chamber in which it is compressed into a rectangular package under the action of a reciprocating plunger. When each package has reached a predetermined length, a tying mechanism is operated to encircle the package with a plurality of strands so as to form a finished bale, which is subsequently ejected from the baler.
Because the discharge end of the baling chamber is at a substantial height above the ground, there is a risk of bales being damaged by their fall from the baling chamber. For example, the impact may result in breakage of some or all of the strands. Commonly this problem has been solved by providing a guide or slide at the exit of the baling chamber for reducing the height from which the bale is released onto the field and/or giving a wanted orientation to the bale. Such apparatus is termed a bale chute, or a discharge chute, and examples are to be found in WO 96/29195 and EP 0771522.
There are constraints on the level of the bale chute above the field. Sufficient clearance should be provided to prevent contact with the ground when one or both wheels of the baler runs into a hole. On the other hand too high an exit level of the chute makes the impact of the bale too great, such that it may fall apart. Even with reduced heights, problems may occur because the bale starts rotating during its fall and the acquired momentum may rotate the bale further after its edge hits the ground, thereby making the bale tip over and putting it to rest on its front end. The consequent mixture of properly deposited and upright bales on the same field later complicates the handling and collection of the bales.
Consequently, a system is needed to ensure the proper and consistent deposit of the bales, without however exposing the bale chute to increased risks of damage by contact with the ground.
A bale chute that meets these requirements is disclosed in EP 0794260. Here, the bale chute is formed in two portions. A front portion is pivoted to the frame of the baler and a rear portion is pivoted to the rear end of the front portion. The rear portion is movable between an upper, bale sustaining, position and a lower, bale discharging, position. In this way, the bale chute can be lowered during the time interval of the actual discharge operation only. During the remainder of the baling operation, the bale chute is kept at a level sufficiently high to preclude collision with the ground.
The bale chute of EP 0794260 needs to be typically one and a half times as long as a bale. The first part, which is as long as a bale, supports a bale as it leaves the baling chamber and the shorter second part tilts and lowers the bale to the ground. The fact that the bale chute is in two parts enables it to be folded away when the baler is in a transport mode while providing a sufficiently long inclined ramp to lower bales gradually to ground level.
In EP 0794260, the front portion can be pivoted between a vertical stowed position and a lowered position in which it is level with the floor of the baling chamber and only the rear portion can be inclined below this level to discharge a bale onto the ground.
During operation, while crop is being compressed in the baling chamber to form the next bale, the last completed bale is retained in the baling chamber to offer resistance to the reciprocating plunger compressing the next bale. The last completed bale emerges incrementally from the baling chamber and is supported on the front portion of the bale chute. To avoid damage to the emerging bale, the front portion of the chute needs to be retained in line with the baling chamber until the bale in the process of being formed has reached the desired size and the emerging bale has left the baling chamber entirely. This front portion of the chute cannot therefore in normal operation be allowed to tilt below the level of the floor of the baling chamber and it is only the rear portion of the chute that is used to lower the bales onto the ground.
In EP 0794260, the discharging of the completed bales from the bale chute takes place automatically until the last bale in a field. Balers comprise a mechanism for ejecting from baling chamber the last formed bale when no new bale is being produced but the last ejected bale then comes to rest on the front portion of the bale chute because there is no new bale being ejected to push it onto the tilting rear portion of the bale chute.
Hitherto, the lowering of the last bale onto the ground has required intervention by the operator. By reversing the baler and braking abruptly, the last bale could be propelled by its inertia onto the rear portion of the chute. Such reversing of the baler is hazardous and not always successful.
Alternatively, the operator would need to descend from his cabin and push the bale manually along the bale chute but this is inconvenient.